Aptamers are single-stranded nucleic acids isolated from random-sequence nucleic acid libraries by selection such as in vitro selection. Many DNA or RNA sequences have been isolated that bind a diverse range of targets, including metal ions, small organic compounds, biological cofactors, metabolites, proteins and nucleic acids. The target versatility and the high binding affinity of both DNA and RNA aptamers, their properties of precise molecular recognition, along with the simplicity of in vitro selection, make aptamers attractive as molecular receptors and sensing elements.
Current methods, techniques and devices used for identifying chemical and biological analytes typically involve capturing the analyte through use of a non-specific solid surface or through capture deoxyribonucleic acids (DNA) or antibodies. A number of known binding agents must then be applied, particularly in the case of biological analytes, until a binding agent with a high degree of affinity for the analyte is identified such as an aptamer. A labeled aptamer (e.g., labeled DNA) must be applied, where the aptamer causes, for example, the color or fluorescence of the analyte to change if the binding agent exhibits affinity for the analyte (i.e., the binding agent binds with the analyte). The aptamer may be identified by studying which of the various binding agents exhibited the greatest degree of affinity for the analytes.
Some problems associated with current methods of chemical and biological agent identification include that a great deal of time and effort is required to repetitiously generate and apply each of the known labeled aptamers, until an aptamer exhibiting a high degree of affinity is found. In addition, once the identification of a high affinity aptamer is made the synthesis of multiple copies for use becomes a challenge. Accordingly, these techniques are not conducive to easy automation. Current methods are also not sufficiently robust to work in environmental conditions, for example, heat, dust, humidity or other conditions that may be encountered, for example, in the field or in a food processing plant. Portability and ease of use are also problems seen with current methods for chemical and biological agent identification.